Corrugated sheet formed material



1965 B. G. BENGTSSON 3,199,963

CORRUGATED SHEET FORMED MATERIAL Filed NOV. 21, 1962 INV ENT OR 20jezyiim/z BY 40m, 644, M Jam ATTORNEYS United States Patent s oiaims.(or. 29-183) In the transport and storing of great quantities of liquidsubstances at a temperature substantially departing from the ambienttemperature, it is of the greatest importance to be able to utilize themechanical strength and volume of the structure, such as a ships hull,wherein the tank or tanks containing the liquid substance are arranged,the shape of the tank or tanks being as far as possible adapted to theshape of the structure, and they are so arranged as to be supported bythe strengthening elements of the structure. In this connection it hasbeen considered if it is possible to provide the structure, such as acontainer or a ship, with internal insulation and line the insulationwith a sealing shell, so that the insulation is not in contact with theliquid. Such proposition has, however, not been successful, due to thedifficulties encountered from the thermal tensions appearing in asealing shell at varying charges of liquid at a temperature which isstrongly departing from the temperature at the outer face of theinsulation. The possibility has been indicated of the use for thispurpose of a corrugated foil, a shell, but it has been found to bediflicult to prepare such a shell in such a manner that the marginaltensions arising will be of a sufiiciently restricted value to beabsorbed by the insulation at important temperature variations and alsoabsorb the relatively big tensions simultaneously appearing in the shellproper due to thermal and/ or hydrodynamic load.

The purpose of the present invention is to provide a corrugated sheetmade of metal or other deformable but shape rigid material which i.a. isadapted for use in a shell as referred to above and wherein the folds orwaves are arranged in such a manner that when the sheet is in the form agenerally flat condition or in a curved condition having a radius ofcurvature which is very great as compared with the amplitude value ofthe corrugations, no essential tensile stress is developed in the sheetalong the plane so formed. When a sheet according to the invention issecured relatively to its environments and at the same time subjected togreat variations in temperature relatively to the ambient temperature,the forces required for the purpose of securing the sheet are to besmall and in all essentials dependent upon the bending strength of thefolds or waves.

According to the invention this is achieved by so forming thecorrugations that they consist of substantially straight wave crestsdeparting in opposite directions from the mean plane of the sheet, theindividual wave crests being so arranged relatively to each other thatthe crests departing in one direction are broken by crests extending atan angle, preferably right angles, to the first mentioned crest and thatthe length of the curve measured along the surface of the sheet betweenany two parallel planes extending at a right angle to the said meanplane, is always essentially the same when measured along two sectionallines in two further parallel planes extending at right angles to themean plane and at right angles to the first mentioned two planes.

Hereby, the individual corrugations may be formed in the most varyingmanners. Thus, the wave crests may be flattened at the top and this topmay be of a very short length along the crest, to such a degree that thewave crest may even present itself in approximately nipple form.Further, the wave crests extending at right Patented Aug. 10, 1965angles relatively to each other may be positioned at different distancesfrom the mean plane of the sheet, and they may be of different width atthe top and/or they may have different side slope angles. Further thehalf wave length, i.e. the distance between the wave crest tops in adirection at right angles to the direction of length of the crests maydiffer. All such various features will be of influence to the propertieswhich are characteristic to each individual sheet, and the choice ofthis or that particular feature will depend upon the material used aswell as upon the intended use of the sheet.

When preparing such a corrugated sheet from a plane or slightly curvedsheet, no portion of the sheet is subjected to any particular tensilestress along the plane proper to such portion, but the bending orfolding operation leads to local bending stresses (effort de flexion) inthe material in a direction transverse to the thickness of the sheet. Ifsuch a sheet is subjected to tensile or compression forces along themean plane of the sheet, such forces will result in that the folds orbends, i.e. the corrugations are slightly straightened or made moreacute, to the effect that no substantial membrane tensions are produced,and consequently no marginal tensions.

It is, however, obvious that in the preparation of a sheet according tothe invention, it is not essential to start with a plane or slightlycurved sheet. It is also possible to prepare the sheet directly with thedesired corrugations by casting, pressing, welding or any other suitablemethod, dependent, i.a. of the material used.

With reference to the accompanying drawing, one practical embodiment ofa corrugated sheet according to the invention is to be described,wherein the wave crests are extending at approximately right angles toeach other. The drawing illustrates a portion of such a sheet.

FIGURE 1 is a perspective view of the sheet.

FIGURE 2 is a sectional view taken along the line A-A of FIGURE 1.

FIGURE 3 is a sectional view taken along the line BB of FIGURE 1.

As shown in the drawing, a sheet formed material is formed with aplurality of mutually parallel wave crests 1 of short length andtransversely to the same a plurality of series of crests 2 of shortlength and lesser height than the former. As shown, the sheet of theexample is formed with a slightly S formed profile of the hill sides ofthe crests 1, so as to give marked wave tops 11 and valley bottoms 12,whereas the hill sides of the crests 2 are approximately rectilinear, insectional view.

Such a double corrugated sheet is capable of absorbing tensile andcompressive forces along the mean plane of the sheet, independently ofthe direction of such forces relatively to the direction of length ofthe individual wave crests, without thereby giving rise to anynoticeable marginal tensions or tensions in the sheet as a whole.

Of the possible fields of use of such a sheet, reference may be made towalls of tanks for the transport or storing of liquified gas, such asmethane or propane at temperatures which are substantially lower thanthe ambient temperature.

I claim:

1. A corrugated sheet made from a flattened sheet of deformable materialhaving three sets of corrugations therein, the corrugations of each setbeing substantially parallel, the corrugations of the first setextending alternately in opposite directions from the mean plane of saidmaterial with wave crests equi-distant from the mean plane of saidmaterial, said second and third sets of corrugations being parallel toeach other and at an angle with respect to said first set ofcorrugations, the corrugations of said second and third sets beingspaced from each other and extending alternately inwardly from said wavecrests in said first set of corrugations onopposite sides of said meanplane respectively, the distance of the wave crests of said second andthird sets of corrugations from said mean planebeing less than thedistance of the wave crests of said first setof corrugations from themean plane, all of said corrugations being formed without elongation ofsaid material, whereby when said sheet is subjected to tensile andcompression forces along its mean plane the angles of said corrugationswill vary without altering the peripheral dimensions of said corrugatedsheet.

2. A corrugated sheet as claimed in claim 1 wherein the wave crests ofsaid first set of corrugations are flattened.

said second and third sets of corrugations are at right angles to saidfirst set of corrugations.

References Cited by the Examiner UNITED STATES PATENTS DAVID L. RECK,Primary Examiner.

3. A corrugated sheet as claimed in claim 1 wherein 15 :HYLAND BIZQT,Examine"-

1. A CORRUGATED SHEET MADE FROM A FLATTENED SHEET OF DEFORMABLE MATERIALHAVING THREE SETS OF CORRUGATIONS THEREIN, THE CORRUGATIONS OF EACH SETBEING SUBSTANTIALLY PARRALLEL, THE CORRUGATIONS OF THE FIRST SETEXTENDING ALTERNATELY IN OPPOSITE DIRECTIONS FROM THE MEAN PLANE OF SAIDMATERIAL WITH WAVE CRESTS EQUI-DISTANT FROM THE MEAN PLANE OF SAIDMATERIAL, SAID SECOND AND THIRD SETS OF CORRUGATIONS BEING PARALLEL TOEACH OTHER AND AT AN ANGLE WITH RESPECT TO SAID FIRST SET OFCORRUGATIONS, THE CORRUGATIONS OF SAID SECOND AND THIRD SETS BEINGSPACED FROM EACH OTHER AND EXTENDING ALTERNATELY INWARDLY FROM SAID WAVECRESTS IN SAID FIRST SET OF CORRUGATIONS ON OPPOSITE SIDES OF SAID MEANPLANE RESPECTIVELY, THE DISTANCE OF THE WAVE CRESTS OF SAID SECOND ANDTHIRD SETS OF CORRUGATIONS FROM SAID MEAN PLANE BEING LESS THAN THEDISTANCE OF THE WAVE CRESTS OF SAID FIRST SET OF CORRUGATIONS FROM THEMEAN PLANE, ALL OF SAID CORRUGATIONS BEING FORMED WITHOUT ELONGATION OFSAID MATERIAL, WHEREBY WHEN SAID SHEET IS SUBJECTED TO TENSILE ANDCOMPRESSION FORCES ALONG ITS MEAN PLANE THE ANGLES OF SAID CORRUGATIONSWILL VARY WITHOUT ALTERING THE PERIPHERAL DIMENSIONS OF SAID CORRUGATEDSHEET.